The following invention relates to a method for determining the content of predetermined ingredients in sliceable products of solid and nonhomogenous consistency, such as foodstuffs, as well as a device for executing the method.
A special measuring method of this type for identifying surface defects in flat objects is known from DE OS 36 01 443. To do so, the transmitted light is captured and metrologically evaluated. The indirect surface contact between the measuring head and the product eliminates the problem of soilage.
A different special measuring method is based on the principle in which monochrome light is beamed into the surface of the merchandise item to be examined. The wavelength of the light is syntonized in a manner that certain molecules of the constituent substances to be determined are excited so that they vibrate. The light that is reflected back is transmitted into the light guide system by the measuring head. The reflected light is then processed via an optical grid in such a way that it can be spectrometrically analyzed.
The light so analyzed provides information about the prevailing content of the ingredient in the product sample that is to be examined.
Since a constant relative motion occurs between the product and the measuring head, stochastically distributed components can also be examined in the product.
The relative motion between the product and the measuring head causes a path-integral measurement to take place at the surface of the product sample, which can then be converted to a volume integral by means of statistical methods.
This principle can be applied in many ways. It is especially suited to monitoring processes in industrial manufacturing, including the sustained monitoring of material compounds, such as bulk materials or liquids.
In addition, the known method allows for both contactless and contact-bound readings.
The contactless measuring method, however, requires that the measuring head which represents the end of the light guide system, remain unobstructedly transparent to light during the entire process.
This cannot be ensured in all methods.
Therefore, the problem that the measuring head may become soiled must be taken into consideration when selecting the measuring method in each particular case.
Alternatively, there is the contact-bound measuring method, such as it is applied in guide rollers for product trains. Here, various measuring heads are distributed over the sleeve of the guide roller to perform the measurements as they come into temporary contact with the outside of the product train as it passes through.
Both measuring methods, however, have disadvantages with regard to certain product types.
For instance, no measuring method is well suited for products of a slightly greasy consistency because of the problem of soil accumulation (=dulling) on the measuring head, which occurs both in the contactless and the contact-bound method.
An important example of an application of this known method is the monitoring of meat processing operations. For products of this kind, the object is to be able to determine a specific level of components within the most narrow tolerances possible, or to obtain it by means of admixing. In sausage production it is for instance necessary to know the fat content of the ground meat beforehand. The stochastic distribution of the fatty materials in the meat is crucial in this instance because the fat is not homogeneously mixed with the meat. This creates the problem of being able to predict the expected result even in the pre-grinding stage.
The aspect of predicting the end result is thus of the greatest importance. To do so, the result must be predictable within a very narrow tolerance. If it is found during the processing of a specific batch that the desired goal cannot be achieved, an adjustment must be made by technical means in order to produce a total batch having the desired content of the respective components, by admixing certain predetermined amounts of ground material from other batches.
It must be expressly noted here that a partial aspect of the invention also consists in the ability to measure different components, such as protein, collagen, water, salts, etc., and to express them in percentages by weight, for example.
Thus, the objective of the invention is to refine the contact-bound measuring method for products that are subject to a process of size reduction so that, with a minimum amount of equipment, it can be applied to the type of product where the dulling of the measuring head has so far been unavoidable.
The invention offers the advantage that the constant surface contact between the measuring head and a surface of the product to be examined prevents the measuring head from becoming dulled.
This advantage is accomplished in that only the complete front face of the measuring head is kept in surface contact with the product while a constant relative movement to the product is maintained.
This keeps greasy particulates which adhere to the surface of the product from settling on the measuring head. As a result of the relative movement between the measuring head and the surface of the product, the entire front face is constantly being wiped clean.
The constant contact during the relative movement creates a cleaning-off effect on the measuring head and ensures a highly accurate and precise measurement.
Another essential feature is the predetermined contact pressure between the measuring head and the product which ensures the wiping effect to keep the front face of the measuring head free of the greasy deposits which would otherwise settle on it.
The constant sliding motion between the front face of the measuring head and the outer surface of the product prevents any undesirable interference during the measuring cycle. The sliding motion, so to speak, automatically ensures that the light intake surface at the front face of the measuring head is kept clean. The self-cleaning effect is thus essential to the invention.
The light from the light guide system can thus enter the product unimpeded, and the light reflected from it can return into the light guide.
It must be expressly noted that the method described in this invention can also be applied for products whose surface consistency is not greasy.
However, due to the self-cleaning effect, the method is particularly suited for product samples of meat-like consistency. Especially in the area of industrial sausage manufacture involving the preliminary size reduction of meat in chunks, the method offers significant advantages. This will be addressed later.
The measuring head rotates either in an oscillating or a unidirectional fashion. This is a refinement that is suited to the lot-by-lot processing of large product batches.
In addition, oscillating measuring heads can be made to execute one empty sweep after each measuring sweep.
This measure is designed to obtain a uniform wiping direction at the front face of the measuring head. The measuring head is thus always swept clean in the same direction. In the opposite direction, no contact between the front face of the measuring head and the product can occur.
Particularly when shredding meat, and preferably frozen meat, the process is very easily integrated into the size reduction process.
It is provided to this effect that the movement of the measuring head be coupled to the movement of the cutting device. Since a measurement is performed simultaneously with each cutting movement at the cutting surface or a surface that is parallel thereto, the result thus is a two-dimensional measuring protocol over the length of the product with each one-dimensional movement of the measuring head.
In addition, several measuring heads can be arranged parallel to each other to produce a three-dimensional network of readings.
The method is particularly suited to fully automated data processing. In this application, the data obtained during the continuous measuring process is evaluated at predetermined intervals.
Since during the continuous measuring process the measuring signal is generated continuously but is constantly changing, the intervals at which the readings are evaluated should be more than 20 milliseconds apart. Since the measuring speed lies at about 20 centimeters per second, a more than sufficiently precise measuring protocol can be expected along the measuring path. A single measurement must be established as a lower limit for each cutting level.
In addition, there should be a capability for performing calibrations in order to allow for the use of the same method for a great variety of products. This also provides the advantage of adjusting worn measuring components, for example.
The method is especially useful when coupled with an admixing procedure.
The objective of an admixing procedure is to obtain an artificial product mix for which the percentage of the ingredient in question is specified.
To do so, the precise percentage of the ingredient in question in each lot within the total batch must be determined. By means of the appropriate numerical integration across the entire volume of the batch it is then possible to predict what percentage of the ingredient will be present.
Any deviation from the desired value can then be corrected by the timely admixture of lots which have a different content.
The invention thus offers the advantage that the great fluctuation ranges that are customary nowadays, such as for example the fat content listed for salami, can be significantly reduced.
The achievable range of fluctuation is expected be significantly less than xc2x11%.
A significant feature in this device is the flush, seamless border shared by the measuring head and the surface of the measuring head bracket which faces the product. Nothing can accumulate on this smooth and continuous surface.
On the one hand, the constant contact with the product by the measuring head reduces the wear and tear of the measuring head to a minimum, while on the other hand the measuring head itself is continuously wiped clean. No clogging of border seams, etc. will occur.
Advantageous refinements are derived from the subclaims.